Test data for players

Discussion in 'Blu-ray & DVD Players & Recorders' started by raigraphixs, Feb 12, 2002.

  1. raigraphixs

    raigraphixs
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    Hi,

    Can someone give me some laymans explanation and ratings on test data marks used buy some mags.

    1. Video Jitter - ns (nanoseconds) the lower the number the better?.
    Explaination:


    2. Siginal to noise -
    Explaination:


    3. Frequency response (s-video) at 5.8mHz; higher or lower ratings are best?
    Explaination:


    4. Chroma AM/PM; higher/lower is better?
    Explaination:




    The reason i ask is that i see in many test data marks the results are very similar, but one player would get better picture marks than another with same test data results. This confuses me a bit. So are they saying test data is one thing, but seeing a dvd player live showing a film is another, though they may score the same, the picture, sound can vary?.


    Also at the moment i have a;
    tosh 2109b (old player) has a video jitter of 3ns, and the image is fantasic, but i would like to have component inputs.

    the new tosh510E has a jitter of 5ns,

    and a highend 900E has a jitter of 2ns.

    what do you make of this, if anything.


    regards


    rai
     
  2. bh

    bh
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    It's here on the HCC website:


    "Video jitter

    Here, we examine variations in the horizontal sync timing of the video signal on a single picture frame. With analogue VCRs, problems manifest themselves as lateral wobble of the picture and/or colour errors at the top of the screen. DVD suffers less from video jitter - even a 'poor' measurement will still be around 500 times better than a good VCR - you're unlikely to see an unstable picture from DVD. Lower jitter readings indicate a solid and mechanically stable transport.

    1 or 2ns: Excellent

    3 or 4ns: Very good

    5 or 6ns: Good

    7ns: Average

    7ns or more: Below average

    Chroma AM/PM

    These measurements set out to determine how good a DVD's colour performance is. Since the colour (chrominance) signal is sensitive to both amplitude (strength) and phase (timing) variations, two separate measurements are made - amplitude-modulation (AM) and phase-modulation (PM). The results are expressed in decibels below reference level. Problems here may result in low-level colour pictures that lack contrast. Look for chroma AM/PM readings of at least -68dB. Poorer performers will show a greater disparity between the AM and PM reading.

    68dB or more: Excellent

    66dB: Very good

    65dB: Good

    60dB: Average

    60dB or less: Below average

    Upper frequency response

    As with TVs and VCRs, this is the highest luminance frequency that can be resolved. Using a special 'multiburst' test DVD, we check the amplitude of the highest-frequency (5.8MHz) burst. The higher the figure the better. We assess both composite and S-video outputs.

    Composite video

    -4.5dB or more: Excellent

    -8.5dB to -4.5dB: Very good

    -9.5dB to -8.5dB: Good

    -10.5dB to -9.5dB: Average

    -10.5dB or less: Below average

    S-video

    -6dB or more: Excellent

    -8.5dB to -6dB: Very good

    -9.5dB to -8.5dB: Good

    -10.5dB to -9.5dB: Average

    -12dB or less: Below average

    Chroma crosstalk

    'S-video' stands for 'separate video' - chrominance and luminance paths are kept separate to aid performance. There is usually a tiny 'leakage' between the two, which can create a low-level 'moire' (colour patterning) effect. This test puts a precise figure on this leakage.

    -61dB or more: Excellent

    -59dB to -61dB: Very good

    -55dB to -59dB: Good

    -50dB to -55dB: Average

    -50dB or less: Below average

    Signal-to-noise ratio

    All electronic systems generate unwanted noise. It's not so much of a problem in the digital domain, but things are rather different when the signals are converted back into analogue. In video systems, noise is apparent as grain or low-level patterning. We measure the levels of noise that are added to a colour-bar pattern derived from a digitally-produced and mastered (it's noise-free) test DVD.

    76dB or more: Excellent

    73dB to 76dB: Very good

    70dB to 73dB: Good

    60dB to 70dB: Average

    60dB or less: Below average

    Digital deviation

    Although sound quality is influenced by many different parameters, audio jitter leads to a lack of musicality or a softening of the bass amongst other things.

    180ps or less: Excellent (audiophile CD standards)

    180ps to 250ps: Very good

    250ps to 350ps: Good

    350ps to 500ps: Average

    500ps or more: Below average

    2,000ps or more: Terrible"


    Source
     

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